A sheet processing apparatus has been developed which combines, as needed, a cutting mechanism, a slit forming mechanism which cuts a sheet in parallel with a sheet conveying direction, and a fold forming mechanism which forms a fold onto the sheet, by cassetting.
FIG. 27 shows a cutting mechanism of a sheet processing apparatus. A cutting mechanism 201 includes an upper movable blade 201a, and a lower fixed blade 201b. The upper movable blade 201a is driven to be raised and lowered to cut sheet N at cutting position P1 in a direction orthogonal to sheet conveying direction F. A pair of conveying rollers 202 including an upper conveying roller 202a and a lower conveying roller 202b are arranged on the sheet conveying upstream side of the cutting mechanism 201. A pair of conveying rollers 203 including an upper conveying roller 203a and a lower conveying roller 203b are arranged on the sheet conveying downstream side of the cutting mechanism 201. In addition, a sheet receiving section 204 is arranged on the sheet conveying downstream side of the pair of conveying rollers 203 on the sheet conveying downstream side.
FIG. 14 shows an example of the array pattern of products Q processed from one sheet N by the sheet processing apparatus. In this array pattern, four products Q having folds are manufactured by a cutting process and a fold forming process. Specifically, the slit forming mechanism cuts sheet N on a plurality of slitting lines E in parallel with sheet conveying direction F to cut away cut regions K at both ends and in the middle in sheet conveying width direction W, the fold forming mechanism forms folds along folding lines G in sheet conveying width direction W orthogonal to sheet conveying direction F, and the cutting mechanism 201 (FIG. 27) cuts sheet N on a plurality of cutting lines C and Cr in sheet conveying width direction W to cut front end cut region (front end margin) Sf, middle cut region Sm, and rear end cut region (rear end margin) Sr.
In processing sheet N in the array pattern in FIG. 14, in the cutting process as shown in FIG. 27, the cut strips in front end cut region Sf and middle cut region Sm after cutting pass through between the cutting mechanism 201 and the pair of conveying rollers 203 on the sheet conveying downstream side to be discharged downward. On the other hand, the cut strip in rear end cut region Sr passes through between the cutting mechanism 201 and the pair of conveying rollers 202 on the sheet conveying upstream side to be discharged downward.
Sheet conveying direction length Lr of rear end cut region Sr is different according to the size, number, and array of products Q. When sheet conveying direction length Lr of rear end cut region Sr is too long, the cut strip in rear end cut region Sr after cutting cannot be discharged downward. For instance, as shown in FIG. 28, when sheet conveying direction length Lr of rear end cut region Sr is longer than distance D1 between cutting position P1 of the cutting mechanism 201 and nipping position P2 of the pair of conveying rollers 202 on the sheet conveying upstream side, the cut strip in rear end cut region Sr after cutting is vigorously fed out in conveying direction F by the pair of conveying rollers 202 on the conveying upstream side rotated at normal conveying speed V1. With this, the cut strip in rear end cut region Sr passes over the lower fixed blade 201b to be stayed on the sheet conveying downstream side of the cutting mechanism 201, is nipped between the pair of conveying rollers 203 on the sheet conveying downstream side to be discharged into the sheet receiving section 204, and is stayed on the lower fixed blade 201b. These phenomena cause sheet jamming and cutting failure.
To eliminate these, as shown in FIG. 29, the present applicants have contemplated a controlling method in which when sheet conveying direction length Lr of rear end cut region Sr is equal to or more than a predetermined value, rear end cut region Sr is finely cut and divided into predetermined fine-cutting unit length Lr0 from the sheet conveying downstream end thereof (Patent Document 1). Predetermined fine-cutting unit length Lr0 is set to be the length to the extent that the cut strip in finely-cut divided region Sr0 can be discharged downward from a gap between the cutting mechanism 201 and the pair of conveying rollers 203 on the sheet conveying downstream side in FIG. 27.